Severe winter weather a likely driver of ‘recent and rapid’ rise in cold-related deaths

Key takeaways:

• Researchers reported a significant increase in cold-related deaths from 1999 to 2022.
• Homelessness, substance abuse and social isolation may contribute to rising cold-related mortality.

Deaths attributed to cold temperatures in the United States more than doubled over the past 2 decades, according to a research letter published in JAMA.

The findings come as heat-related deaths in the country have also significantly risen in the last several years, showing the significant and deadly effects of climate change on public health.

“Although mean temperatures are increasing in the U.S., studies have found that climate change has been linked with more frequent episodes of severe winter weather in the U.S. over the past few decades, which may in turn be associated with increased cold-related mortality,” Michael Liu, MPhil a research fellow at Beth Israel Deaconess Medical Center, and colleagues wrote.

However, there is a lack of understanding on the exact burden of cold-related deaths and how they vary by populations and geographic locations, they added.

In the study, the researchers used CDC’s WONDER platform to evaluate death certificates from 1999 to 2022 and determine which could be attributed to cold-weather causes.

The analysis calculated age-adjusted mortality rates (AAMRs) per 100,000 person-years for cold-related deaths during each year.

Results showed a total of 63,550,429 deaths in the U.S. between 1999 and 2022, of which 40,079 deaths had causes related to cold temperatures.

The AAMR increased from 0.44 (95% CI, 0.42-0.47) in 1999 to 0.92 (95% CI, 0.88-0.95) in 2022, for an increase of 109%.

Meanwhile, investigators reported a 3.4% (95% CI, 2.4%-4.3%) annual percentage change (APC) in the AAMR over the study period, with a nonsignificant increase from 1999 to 2017 and a significant annual increase from 2017 to 2022 (APC = 12.1%; 95% CI, 6.3%-27.1%).

Liu and colleagues noted that results remained consistent when cold was specified as the underlying cause of death only, with a significant annual increase from 2016 to 2022 (APC = 9.1%; 95% CI, 3.1%-27.9%).

The AAMR in 2022 appeared highest among adults aged 75 years or older (4.23; 95% CI, 3.97-4.49), who “are more susceptible to cold weather due to limited thermoregulatory response and greater prevalence of chronic conditions,” the researchers explained.

However, adults aged 45 to 74 years experienced the largest annual increase (APC = 4.8%; 95% CI, 3.7%-5.6%) between 1999 and 2022.

Men had a greater AAMR vs. women, but “both groups experienced significant increases over the study period,” Liu and colleagues pointed out.

Among diverse populations, researchers observed the highest AAMRs in 2022 among American Indian or Alaska Native (6.26; 95% CI, 5.25-7.27) and Black (1.5; 95% CI, 1.38-1.62) individuals, whereas the largest APCs during the study period occurred among Hispanic (4.1%; 95% CI, 3.2%-5.3%) and white (3.9%; 95% CI, 2.9%-4.7%) subjects.

Such findings are “consistent with the disproportionate exposure of racial and ethnic minority groups to structural risk factors such as lack of home insulation or heat,” Liu and colleagues wrote.

The Midwest had the highest AAMR (1.41; 95% CI, 1.32-1.49) in 2022 and the largest APC increase (4.3%; 95% CI, 2.8%-5.6%) from 1999 to 2022 among all regions.
Researchers identified a couple of study limitations, which included a lack of data on individual-level risk factors and possible underreporting of cold-related deaths.

The potential drivers of the results should be researched further “and may include more frequent extreme winter weather events and/or the rising burden of risk factors for cold-related mortality such as homelessness, social isolation, and substance use,” Liu and colleagues wrote.

“The recent and rapid increase in cold-related deaths warrants public health interventions to improve access to warming centers and indoor heating for vulnerable populations,” they concluded.